Electromagnetic horn



Sept. 24, 1929. F. F. DoRsEY ELECTROMAGNETIC HORN Filed July 16, 1926llmrmfwm' Fig@ UNITED STATE FFICE 4 FABNUM F. DORSEY, 0F ROCHESTER, NEW'YORK, ASSIIGNOR T0 NORTH EAST ELEG- TRIG COMPANY, OF ROCHESTER, NEWYORK, A CORPGEATION F NEW YORKA ELEGTRQMAGNETIC HORN Application ledJuly 1,

The invention relates to electromagnetic horns or sound signals of thekind in which a diaphragm is vibrated by the action of an electromagnet.ln such horns the coil by which the magnet is energized is usuallycontrolled by a circuit-breaker moved by engagement with the armature orsome other vibrator member of the horn.

rlhe o ject of the invention is to provide a circuit-breaker of simple,compact and inexpensive form for embodiment in a horn of the typereferred to, and to provide simple and convenient means for adjustingthe operative position of the circuit-breaker. More particularly, anobject of the invention is to produce a circuit-breaker which is adaptedin form to the restricted space within the body of such a horn at oneside of a magnet having a centrally located core and winding. To theforegoing ends the invention consists in the circuit-breaker hereinafterparticularly described, as it is dened in the appended claims. Q

1n the accompanying drawings, Fig. 1 is a side-elevation, partly inmedian section, of a Ahorn embodying the present invention. Fig. 2 is aplan-view of the same horn with the upper portion of the housing brokenaway to show the interior parts, and Fig. 3 is a frontelevation of thehousing and the parts fixed to and inclosed within it, the vibratorymembers and the forward portion of the horn being removed.

The invention is illustrated as embodied in .a horn having a diaphragm 5of thin sheet metal, which may be corrugated, as shown, to impart to it,the necessary stiffness. This diaphragm is clamped, at its margin,between a front plate 6 and a body shell or housing 7. The diaphragm isactuated by an electromagnet having a core 8 which is surrounded by acoil or winding 9. The magnet comprises, also, a generally U-shapedmember 36, which embraces the winding and h' .s polar'extremities 37 oneither side thereof.

The magnet cooperates with an armature in the form of a flat steel bar10, which is ixed to the middle of the diaphragm by meansof a screw orbolt 11, a spacer 12 being interposed 80 between the armature and thediaphragm.

ieee. semi No. 122,812.

Theihousing 7 has a dat rear wall constil for use in a horn having aconstruction such as that just described. rlhis circuit-breakercomprises a blade-spring, 13 of thin and A resilient steel or othersheet metal, and a movable contact 14 carried by the blade-spring. Astationary contract 15 cooperates with the movable contact. Theblade-spring and the stationary contact `are both supported by a memberwhich is normally stationary but which may be moved, through a slightdistance, to adjust 'the operative position of the circuit-breaker.rlhis stationary support is shown as having the form of a singleelongated blank of sheet metal, comprising a part 16 extending parallelto the axis of the casing and ixed, at its rear end, to the plate 19 bymeans of screws. These screws engage a bent extension 17 at the rear endof the part 16. At the front end of the part 16 the support is bent at aright angle so as to provide a part 20 substantially parallel with thediaphragm. At its middle 'portion the part 20 has an upwardly extendinglug 21, and the bladespring 13 is secured t0 this lug by rivets 22 butis insulated from the lug by interposed insulating material, as shown inFig. 1. A terminal 23 is secured in place against the bladespring, bymeans of the same rivets 22, an'd `through a wire 32 this terminal isconnected with a binding-post 33.

The stationary contact 15 is fixed to the middle of a plate24 ofinsulating material, and this plate is riveted, at its ends, to the part20 of the support. A terminal 25, engaged by the contact 15, isconnected to one terminal of the coil 9, as shown in Fig. 1. The otherterminal 34: of the coil is connected with the other binding-post 35.

The su port is made of sheet metal which While su stantially thicker andmore rigid than that of the blade-spring 13, is still ilexible enough topermit a movement by which the operative position of the blade-springand the contacts may be adjusted. The blade-spring projects radiallytoward the axis of the magnet, and its inner end lies behind thearmature 10 and is adjusted at a position in which it will be engagedand moved by the armature at each rearward vibration, so as to cause thecontact 14 to be disengaged from the contact 15 and thus to break thecircuit through the magnet. The adjustment in question is effected bymeans of a screw 26, which engages the rear surface of the support andis threaded into a sleeve 28, iixed to the rear wall or plate 19, thehead 29 of the screw extending to the outside of the housing so as to bereadily accessible. spring to a position nearer the normal position ofthe armature, this is accomplished by turning the screw in a directionto move the support forwardly. This movementoccurs chiefly in the part20 and is permitted by bending of the support, particularly in the part16. To facilitate and localize such bending, and at the same time topermit the use of relatively thick and iirm material in the support, itis preferable to provide a transverse notch 27 in the part 16 toincreasethe iiexibility of the material at this point.

The resiliency of the metal may keep the support in engagement with thescrew 26, and this screw rigidly resists rearward bending of the supportwhen the blade-spring is engaged and bent rearwardly by the armature. Toprevent the possibility of looseness in the parts, however, it isdesirable to use a spring to hold the support firmly against the screw2.6, and for this purpose a coil-spring 3Q may be used as shownparticularly in Fig. 2, one end of the spring being attached to thelower end of the support while the other end is attached to an eye 31fixed to the plate 19.

It will be apparent that 'the construction just described provides, inasimple and eff ective manner, for the adjustment of thecircuit-breaker, while at the same time it perm1ts no vibration in anyof its parts. The extensionlof the adjusting screw through the rear wallof the housing makes it conveniently accessible for the purpose ofadjustment, while vthe constant spring pressure agalnst the screw in onedirection causes the screw to be held frictionally against anyaccidental rotation while the horn is in use.

N A piece of insulating material 38, xed to the rear surface of thearmature, prevents direct engagement between the metal of the armatureand that of the blade-spring, and by this meanstogether with theinsulation of the two contacts, the electric circuit is entirelyinsulated from the mechanical parts of the horn. 'f

If it be desired to adjust'the blade` The invention claimed is:

1. In an electromagnetic horn comprising a diaphragm, an armatureattached thereto, and an electromagnet .cooperating with the armatureand having a core concentric with the diaphragm, a circuit breaker, forcontrolling the magnet, comprising; a movable contact, a relativelyflexible blade spring, 011 which the movable contact is mounted,arranged with its length substantially radial with respect to the axisof the magnet and with its inner end lying in the path of movement ofthe armature so as to be engaged and moved thereby, a stationary Contactcooperative with the movable contact, an adjustable stationary' support,for theblade-spring and the stationary contact, comprising an elongatedmember of sheet-metal to which the stationary contact and the outer endof the blade-spring are rigidly attached, but from which 011e at leastof them is insulated, said member arranged with its length substantiallyat a right angle with the length of the blade-spring, and screw-threadedmeans engaging one end of said support and operable to move the supportin the general direction of movement of the movable contact so as toadjust the operative position of the bladespring; in combination with arigid stationary member of the horn to which the other end of thesupport is rigidly attached, the support consisting ofmaterial'substantially stiffer than the blade-spring so as nottoparticipate in the operat-ive movement thereof, but being sufficientlyflexible to permit bending, at the part between its fixed end and the'point of attachment of .the blade-spring, so as to permit angulardisplacement of the support by the screw-threaded adjusting means.

2. In an electromagnetic horn having a diaphragm, an armature attachedto the diaphragm in therear thereof, a stationary plate 1n the rear ofthe armature, and a magnet supported by said plate and having a coreconcentric with and projecting toward the diaphragm: a circuit-breaker,for controlling the magnet, comprising a continuous strip of resilientsheet-metal attached at one end to said plate, projecting forwardly fromthe late but bent, at a substantial distance thererom, at asubstantially right angle and extending thence substantially parallelwith and between the plate and the diaphragm and alongside the magnet,adjusting means engaging the free end of said strip, for moving said endin a direction normal to the plate, a stationary contact mounted on butinsulated from said strip, a movable contact cooperative with thestationary contact, a bladespring carrying t-he movable contact andattached, at its outer end, to said strip but insulated therefrom, saidspring extending radially toward the axis of the diaphragm with itsinner end in the path of movement of the armature, and a body ofinsulating material interposed between the spring and the armature andattached to one of these parts.

3. In combination With a stationary member of an electromagnetic horn, acircuitbreaker comprising a strip of resilient sheetmetal attached, atone end, to said stationary member, means engaging the strip, at a pointremote from its point of attachment, for bending the strip to adjust itsposition, a blade spring attached to said strip and projecting beyondone side-edge thereof, and cooperative contacts mounted respectivel onthe strip andthe blade-spring, one at east of said contacts beinginsulated from the member on Which'it is mounted.

FARNUM F. DORSEY.

